Background/Aim: Although osteoblasts are thought to be the major component of the hematopoietic stem cell niche in the bone marrow microenvironment, the role of osteoblasts in hematopoiesis is still unclear. The ability of human osteoblasts to support early hematopoiesis was investigated. Methods and Results: Human CD34+ bone marrow cells cultured on human osteoblasts were capable of surviving without addition of cytokines and differentiated into myeloid cells with slight proliferation. The results of immunohistochemical experiments suggested activation of FAK and AKT in hematopoietic cells attached to osteoblasts. When stem cell factor, Flt3-L, and IL-3 were added to the coculture system, each cytokine distinctively enhanced proliferation and differentiation of CD34+ bone marrow cells. Conclusion: The results suggest that human osteoblasts have the ability to support hematopoietic cell development in vitro.